Methods for winding a stator coil for a rotary electric machine include a concentrated winding method in which a coil is wound on each magnetic pole in a concentrated manner and a distributed winding method in which winding is performed over a plurality of magnetic poles. With the distributed winding method, the distribution of a rotation magnetic field becomes smooth as compared to that with the concentrated winding method. Thus, the distributed winding method has a merit in which vibration during operation of the rotary electric machine can be reduced.
Meanwhile, at a coil end portion of a stator coil wound by the distributed winding method, a plurality of wires overlap each other, and thus the height of the coil end portion is increased in the axial direction, which hinders size reduction of a rotary electric machine.
Therefore, there is the following winding method as one means for optimizing the manner in which the wires overlap each other at the coil end portion in the distributed winding method and minimizing the gaps between the wires overlapping each other, thereby reducing the height of the coil end portion. In this winding method, each stator coil for one phase is initially divided into a plurality of coils, and these division coils are assembled to a stator core and then joined together.
In other words, in this winding method, a portion of each division coil that is to be a coil end portion is formed in advance into such a shape as to minimize gaps when a plurality of coils overlap each other, and these division coils are assembled to the core, whereby waste gaps in the coil end portion are reduced and the height of the coil end portion is reduced.
In this case, assembling in an optimum shape is made possible by division into a plurality of coils, although assembling to the core is very difficult if an integrated coil is formed with an optimum coil end shape without being divided.
When this method is adopted, a stator coil is formed by joining the division coils together after the division coils are assembled. At this time, when the height of a joint portion is large, the height of a coil end also becomes large accordingly, so that there is a problem that the length in the axial direction of a rotary electric machine is increased.
As a countermeasure for this, in the conventional art, a configuration has been proposed in which joint portions of division coils are disposed at the radially inner side and the radially outer side of a coil end to expand the positions of the joint portions in the radial direction, thereby preventing an increase in height in the axial direction (see, for example, Patent Document 1 below).